The purpose of this protocol is to determine the phase II response rate of melanoma and renal cell cancer to therapy with Topotecan, a topoisomerase I inhibitor and to determine whether granulocyte-macrophage colony stimulating factor (GM-CSF) given before chemotherapy prevents myelosuppression. All patients receive Topotecan 1.5 mg/m2 daily by bolus intravenous infusion for five days and post-therapy GM-CSF 250 ug/m2 daily. Patients are randomized to receive no additional therapy or GM-CSF 250 ug/m2 twice daily before Topotecan. Twenty-one patients have been entered on study, nine patients with melanoma and twelve with renal cell cancer. Sixteen patients are evaluable for response, eight with melanoma and eight with renal cell cancer. No responses have been seen. One patient with renal cell cancer had complete regression of his lung metastases but no response in his kidney primary. A decrease in grade IV neutropenia following the first cycle of Topotecan has been seen. One of seven patients treated with pretherapy GM-CSF in addition to post therapy GM-CSF experienced grade IV granulocytopenia whereas eight of eleven patients who received GM-CSF only after chemotherapy had grade IV granulocytopenia.